The aging process results in lost capacity to respond to environmental and toxicological stresses, increasing morbidity and mortality in the elderly. In particular, glutathione (GSH) levels decline and GSH-dependent detoxication mechanisms are attenuated, leading to markedly increased susceptibility to oxidative stress, drugs and xenobiotics. The mechanism(s) involved in this age-related impairment are unclear but may be due to altered transcriptional regulation of gamma-glutamylcysteine/igase (GCL), the rate controlling enzyme for GSH synthesis. GCL gene expression is largely controlled by Nrf2, a transcription factor that binds as a heterodimer to the antioxidant response element (ARE), a conserved DNA sequence found in the promoter region of GCL and most GSH-dependent detoxication genes. We recently showed that (R)-alpha-Iipoic acid (LA) reversed not only the basal loss of hepatic GSH in old rats, but also the increased susceptibility to xenobiotic insult. Thus our central hypothesis is that Nrf2-dependent transcriptional control of GCL is compromised with age, but LA treatment reverses this loss. This hypothesis will be explored in the following specific aims: Aim 1: Determine the optimal LA dose to induce expression of GCL. We will establish both the optimal concentration and time-course for LA to maximally induce Nrf2-mediated gene expression of GCL. These studies will be necessary to explore both the mechanisms (Aim 2) leading to the age-related loss of Nrf2- mediated gene expression as well as how LA reverses this loss. Aim 2: Assess how LA reverses the age-associated loss of Nrf2-mediated transcriptional control. This aim will be explored by determining 1) the age-dependent changes in the nature and composition of the Nrf2 transcriptosome, 2) whether LA acts to induce upstream cell signaling pathways that cause Nrf2 phosphorylation and subsequent nuclear translocation and 3) whether LA directly activates Nrf2-dependent transcription by initiating release of Keap-1, a cytosolic protein normally bound to Nrf2 that prevents its nuclear translocation. Aim 3: Monitor whether LA reverses the age-associated increased vulnerability to toxicological insult. We will explore whether LA pre-treatment increases resistance to acetaminophen both in vitro and in vivo. Thus, the successful completion of the proposed studies will lead to a precise understanding how LA regulates Nrf2-mediated gene transcription and whether it improves resistance to toxicological insult in the elderly.